Our invention relates to broken rail detecting track circuit for railroad track sections in which parallel circuit paths exist for track circuit current. More specifically, the invention pertains to improved circuit arrangements which supplement the normal track circuits for more assuredly detecting broken rails in sections of railroad track having parallel circuit paths, e.g. dual gage track.
Broken rail detection is a desirable feature of any railroad track circuit system. Generally, in the usual two rail track, a conventional track circuit provides broken rail detection which is adequate and reliable. However, under certain conditions, commonly used track circuits do not, without added measures, always detect broken rails. Track sections in which lengths of rail are electrically paralleled present additional and unique problems. For example, dual gage track circuits, as shown in the cited Staples application, utilize the two rails unique to the narrow and wide gages connected in parallel with the common third rail as the return path. A break in one of these two so-called other rails, i.e., not the common rail, is bypassed by current flow in the multipled other gage rail. It has been previously proposed, e.g., the Staples application, to use a separate audio frequency (AF) circuit in the closed loop formed by the two other rails in parallel. Even then, depending upon various track characteristics and parameters, a broken rail may be bypassed by alternate current paths with the possibility of sufficient signal pick up at the receiver to retain a safe condition registry. An economic advantage accrues if the separate AF circuit can be eliminated, at least under favorable conditions, by using the train detection track circuit current in broken rail detection. Another situation which creates similar problems is a guard rail closely spaced along a length of a running rail and which may have electrical bond connections to the running rail at least at each end of the length of guard rail. An even further problem exists where dual gage switches create the possibility of a shunt fault between the two other rails to complicate the detection of a broken rail. A shunt fault may also occur between a running rail and an associated guard rail to cause additional sneak circuit paths which circumvent broken rail detection. A supplemental or modified broken rail detection arrangement is thus needed.
Accordingly, an object of our invention is an improved circuit arrangement for detecting broken rails within a railroad track section.
Another object of the invention is track circuit apparatus for detecting a broken rail within a track section in which lengths of the rails are electrically connected to form parallel circuit paths.
It is also an object of the invention to supplement the train detection track circuit with apparatus to provide broken rail detection for track sections where alternate circuit paths may exist to bypass any broken rails and prevent detection by the regular track circuit.
A further object of the invention is circuit apparatus for a railroad track section, in which rail lengths are electrically connected in parallel, which uses current from the train detector track circuit to also detect broken rails.
Yet another object of our invention is an improved broken rail detection for a dual gage railroad track, utilizing energy already present in the rails for train detection.
It is another object of our invention to provide reliable broken rail detection for a section of track with parallel electric circuit paths in which shunt faults may occur at intermediate points between the paralleled conductors.
A still further object of the invention is a track circuit arrangement for assuredly detecting broken rails in a dual gage track section in which track turnouts exist.
Another object of the invention is broken rail detection circuitry, for a dual gage railroad section with turnouts and track switches, including comparison apparatus actuated by train detector track circuit energy and other apparatus actuated by separate and distinctive AF energy.
Other objects, features, and advantages will become apparent from the following specification and appended claims when taken with the accompanying drawings.